With the ever-increasing number of contaminated rivers, ponds, estuaries and diminishing number of natural potable water supplies, we are quickly realizing the cumulative impact wastewater has on our natural resources. The degradation of water quality from wastewater discharge is a global issue that is intertwined with population growth. The eutrophication of our coastal systems has become an environmental crisis quickly gaining the attention of the public. There has been an increase in harmful algal blooms “Red Tide”, which decimate local shell fish beds and result in fish kills. There has also been an increase in what are known as “dead zones” in where the nutrients released from untreated and/or partially-treated wastewater supports a radical growth of the algae resulting in depleted oxygen levels in the waters and a devastating imbalance in coastal ecosystems. The most recent data reported by the United Nations have identified 150 sites classified as “Dead Zones”. It has become apparent the measures taken to protect our natural resources today, will determine the quality of life for future generations.
Conventional wastewater nitrogen removal techniques are incapable of providing a cost effective solution, or fail to remove a significant amount of total nitrogen within a single system. Most existing systems try to accomplish nitrogen removal in a single pass application.
In the wastewater industry it has become common knowledge that through biological treatment the ammonium ions found in wastewater can be converted to nitrite and nitrate ions by organisms living in aerobic zones where, subsequently, the nitrate can be introduced into a second zone where they can be then converted into harmless nitrogen gas by organisms found in the anaerobic zones. For the nitrification process to occur, a sufficient level of alkalinity is required within the aerobic zones. Without sufficient levels of alkalinity the complete conversion from ammonium ions to nitrate can not take place, thereby preventing the subsequent conversion of the nitrate to nitrogen gas to occur, resulting in the release of ammonium ions into groundwater sources and ultimately coastal waters where they are eventually converted to nitrate and contribute to nitrogen pollution and nutrient overloading of coastal embayments.
The second phase for biological nitrogen removal, denitrification, occurs when nitrate ions are converted to nitrogen gas within anaerobic conditions and similarly requires an organic carbon source in sufficient quantities. Additionally, without a sufficient amount of organic carbon available, the reaction can not reach completion, again, resulting in the release of nitrates into the groundwater and ultimately coastal waters.